The present invention concerns a recording apparatus having both a stencil printing function suitable for a great number of sheets and a recording function suitable for a small number of sheet printing.
An existent stencil printing apparatus uses a heat sensitive stencil sheet comprising a thermoplastic resin film layer laminated on a porous substrate. For perforating a heat sensitive stencil sheet, a heating means such as a thermal head having a plurality of dot-like heat generating bodies has been used for example. The heat generating bodies of the thermal head and the stencil sheet are moved while being in contact relative to each other and character image information is given in the form of electric signals to the thermal head in synchronization with the movement. The heat generating body of the thermal head generates heat selectively to melt and puncture the stencil sheet and forms punctured images corresponding to the character image information onto the stencil sheet.
The perforated stencil sheet is wound around a drum of a stencil printing apparatus. An ink supplying device is disposed to the inside of the drum. The drum is rotated and, at the same time, ink is supplied to the inner circumferential surface of the drum and, further, printing paper is fed between a roller disposed away from the drum and the drum. Ink passes through an ink passing portion of the drum and the punctured portion of the stencil sheet to the printing paper, by which images corresponding to the punctured images of the stencil sheet are printed on the printing paper. The preparing/printing method or apparatus as explained above has already been proposed as a digital printing machine and has been popularized as a recording apparatus at a low running cost.
The digital printing machine is used in a case of printing a number of identical printed matter simultaneously but, if the number of printing sheets is small, the printing cost is rather increased since the cost of the stencil sheet per sheet of the printed matter requires a high cost. For obtaining a small number of printed matter, there is a method of directly recording by a thermal head of a digital printing machine to heat sensitive recording paper or heat sensitive transfer recording paper, but incorporation of the heat sensitive recording paper or heat sensitive transfer recording paper in the printing machine has a drawback of enlarging the printing machine and complicating the operation of providing both printing paper for stencil printing and recording paper with small number of printing.
Further, a composite type printing apparatus has also been proposed which combines different printing methods of using only one kind of common paper for the printing paper, conducting electrophotographic printing in a case where the number of printing sheets is small and conducting printing by using heat sensitive stencil sheet in a case of a large number of printing sheets, but it has a drawback that the entire system is complicated, expensive and enlarged in the size.
On the other hand, in a case of obtaining colored printed matter by the digital printing machine, an ink-charged drum has to be provided for each of colors, and it requires a troublesome operation of exchanging the drum upon printing each color with the drum of the corresponding color also in a partial color printing, to worsen the efficiency.
An object of the present invention is to provide a small-sized recording apparatus capable of overcoming the foregoing problems in the prior art and obtaining printed matter of multiple colors from a small number of sheets to a large number of sheets at a low running cost.